1. Field of the Invention
The present invention relates generally to a disk drive of the perpendicular magnetic recording system, and more particularly to a technology for testing the magnetization of a write head.
2. Description of the Related Art
In general, the write head of a disk drive of the perpendicular magnetic recording system is made of a single pole type head because this type of head is suitable for perpendicular magnetic recording.
After the write head of the disk drive writes data signals in a disk medium by perpendicular magnetic recording, the application of a recording current applied to the write head is stopped, but the write head is kept magnetized due to the remanent magnetization.
The remanent magnetization may cause undesirable phenomena after the write operation. For example, the recording data recorded in a data sector of the disk medium and the servo data recorded in a servo sector of the disk may be undesirably erased due to the remanent magnetization. This problem does not occur in the case of disk drives of the longitudinal magnetic recording system.
To solve the problem, the prior art proposes a data write circuit that incorporates a degaussing signal generator for removing the remanent magnetization of the magnetic head (see Jpn. Pat. Appln. KOKOKU Publication No. 5-84564, for example). The degaussing signal generator serves to decrease the write current at a fixed time constant in accordance with the fall of data after the write gate is closed. The prior art also proposes a disk drive provided with a read/write channel including a degaussing signal generator (see Jpn. Pat. Appln. KOKAI Publication No. 7-134804, for example).
As can be seen from the above, it is advantageous if a disk drive incorporates a degaussing signal generator for removing the remanent magnetization of the write head. It is further advantageous if the disk drive has a function of automatically executing a test for detecting the magnetized state of the write head. Where this function is incorporated as part of the SMART (Self-Monitoring Analysis and Reporting Technology System) function, i.e., one of self failure diagnosing functions applied to a disk drive, the host system can control the magnetized state of the write head.